110 lines
7.3 KiB
HTML
110 lines
7.3 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="SQLException" />
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<meta name="abstract" content="The SQLException class and its subtypes provide information about errors and warnings that occur while a data source is being accessed." />
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<meta name="description" content="The SQLException class and its subtypes provide information about errors and warnings that occur while a data source is being accessed." />
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<meta name="DC.Relation" scheme="URI" content="exceptin.htm" />
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<meta name="DC.Relation" scheme="URI" content="sqlwarng.htm" />
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<meta name="DC.Relation" scheme="URI" content="datatruk.htm" />
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<meta name="DC.Relation" scheme="URI" content="exceptionexample.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="exceptions" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>SQLException</title>
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</head>
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<body id="exceptions"><a name="exceptions"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">SQLException</h1>
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<div><p>The SQLException class and its subtypes provide information about
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errors and warnings that occur while a data source is being accessed.</p>
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<p>Unlike most of JDBC, which is defined by interfaces, the exception support
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is provided in classes. The base class for exceptions that occur while running
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JDBC applications is SQLException. Every method of the JDBC API is declared
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as being able to throw SQLExceptions. SQLException is an extension of java.lang.Exception
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and provides additional information related to failures that happen in a database
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context. Specifically, the following information is available from an SQLException:</p>
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<ul><li>Text description</li>
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<li>SQLState</li>
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<li>Error code</li>
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<li>A reference to any other exceptions that also occurred</li>
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</ul>
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<p><a href="exceptionexample.htm">ExceptionExample</a> is
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a program that properly handles catching an (expected in this case) SQLException
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and dumping all the information that it provides.</p>
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<div class="note"><span class="notetitle">Note:</span> JDBC provides a mechanism where exceptions can be chained together.
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This allows the driver or the database to report multiple errors on a single
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request. There are currently no instances where the native JDBC driver would
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do this. This information is only provided as reference and not a clear indication
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that the driver never does this in the future however.</div>
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<p>As noted, SQLException objects are thrown when errors occur. This is correct,
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but is not the complete picture. In practice, the native JDBC driver rarely
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throws actual SQLExceptions. It throws instances of its own SQLException subclasses.
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This allows you to determine more information about what has actually failed
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as is shown below.</p>
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<div class="section"><h4 class="sectiontitle">DB2Exception.java</h4><p>DB2Exception objects are not thrown
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directly either. This base class is used to hold functionality that is common
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to all JDBC exceptions. There are two subclasses of this class that are be
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the standard exceptions that JDBC throws. These subclasses are DB2DBException.java
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and DB2JDBCException.java. DB2DBExceptions are exceptions that are reported
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to you that have come directly from the database. DB2JDBCExceptions are thrown
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when the JDBC driver finds problems on its own. Splitting the exception class
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hierarchy in this manner allows you to handle the two types of exceptions
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differently.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">DB2DBException.java</h4><p>As stated, DB2DBExceptions are
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exceptions that come directly from the database. These are encountered when
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the JDBC driver make a call to the CLI and gets back an SQLERROR return code.
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The CLI function SQLError is called to get the message text, SQLState, and
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vendor code in these cases. The replacement text for the SQLMessage is also
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retrieved and returned to you. The DatabaseException class causes an error
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that the database recognizes and reports to the JDBC driver to build the exception
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object for.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">DB2JDBCException.java</h4><p>DB2JDBCExceptions are generated
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for error conditions that come from the JDBC driver itself. The functionality
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of this exception class is fundamentally different; the JDBC driver itself
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handles message language translation of exception and other issues that the
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operating system and database handle for exceptions originating within the
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database. Wherever possible, the JDBC driver adheres to the SQLStates of the
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database. The vendor code for exceptions that the JDBC driver throws is always
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-99999. DB2DBExceptions that are recognized and returned by the CLI layer
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often also have the -99999 error code. The JDBCException class causes an error
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that the JDBC driver recognizes and builds the exception for itself. When
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run during development of the release, the following output was created. Notice
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that the top of the stack contains DB2JDBCException. This is an indication
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that the error is being reported from the JDBC driver prior to ever making
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the request to the database. </p>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="exceptionexample.htm">Example: SQLException</a></strong><br />
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This is an example of catching an SQLException and dumping all the information that it provides.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="exceptin.htm" title="The Java language uses exceptions to provide error-handling capabilities for its programs. An exception is an event that occurs when you run your program that disrupts the normal flow of instructions.">Exceptions</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="sqlwarng.htm" title="Methods in some interfaces generate an SQLWarning object if the methods cause a database access warning.">SQLWarning</a></div>
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<div><a href="datatruk.htm" title="DataTruncation is a subclass of SQLWarning. While SQLWarnings are not thrown, DataTruncation objects are sometimes thrown and attached like other SQLWarning objects. Silent truncation occurs when the size of a column exceeds the size specified by the setMaxFieldSize statement method, but no warning or exception is reported.">DataTruncation and silent truncation</a></div>
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</div>
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</div>
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</body>
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</html> |